Dendrochronological research

Welcome to dendrochronological www pages of Department of Geology, University of Helsinki!

Dendrochronology is the study of annual rings of trees, tree-rings. Main principle of dendrochronology is cross-dating. Dendrochronologists analyze tree-rings by their common growth behaviour and, as initial step of each analyses, cross-match the wide and narrow tree-rings among the array of samples. One tree-ring chronology consists of tens or hundreds, even thousands, of individual tree-ring series of the same species from a given region. Series are averaged annually to form reliable records of past growth changes. Subsequent to cross-dating, tree-ring chronology becomes dated with absolute accuracy. Climatic and environmental factors influence the growth of tree-rings from inter-annual to millennial time-scales. This creates possibility to date the past climatic and environmental events with highest possible precision of all geological records!

Current tree-ring oriented research at the Department of Geology includes wide spectrum of dendrochronological science. The study of subfossil tree-rings has for long been the speciality of the research group. Scots pine (Pinus sylvestris L.) megafossils remain preserved in the bottom sediments small lakes, peat bogs and as dead standing trees (snags). Additional tree-ring material can be obtained from historical buildings. Theory of cross-dating is a key to built composite chronologies from living, historical and subfossil tree-rings. Megafossil collection from northernmost Lapland covers the past 76 centuries being one of the longest continuous tree-ring chronologies in the world. At the same time, this chronology is probably the longest absolutely dated and annually resolved temperature proxy record. Sample collection has been made in intensive collaboration with the Finnish Forest Research Institute and SAIMA Centre for Environmental Sciences.

The basis of our dendrochronological research is the compound interpretation of living tree and subfossil tree-rings, their variability and factors behind their behaviour. The research can be divided into several different subfields as follows:

1) Dendrochronology: constructing new tree-ring chronologies

2) Dendroclimatology: studying the relationships between tree-rings and climate

3) Dendroecology: studying the relationships between tree-rings and ecological factors

4) Palaeoclimatology: reconstructing the past climates using tree-ring chronologies

5) Palaeoecology: interpreting the past environments from tree-ring based records

6) Time-series analysis is used in all aforementioned (1-5) subfields of dendrochronology. Students aiming for dendrochronological thesis (Bachelor, Master, Licentiate or Ph.D.) should familiarize himself/herself with at least the basic concepts of time-series analysis!

Recent research has been carried out mostly by Emeritus Professor Matti Eronen, Samuli Helama, Jari Holopainen and Marc Macias Fauria (currently at the Biogeoscience Institute of the University of Calgary). Please contact one of us for further information!

Doctoral dissertations

May 2008
"Ecological processes and large-scale climate relationships in northern coniferous forests"
Marc Macias Fauria

November 2006

"Reconstructions of past climates from documentary and natural sources
in Finland since the 18th century"
Jari Holopainen

June 2004
"Millennia-long tree-ring chronologies as records of climate variability in Finland"
Samuli Helama

November 2002
"Tree-ring dating in Estonia"
Alar Läänelaid

Essential text-books about tree-ring for students

Vaganov E.A., Hughes M.K. & Shashkin A.V. 2006: Growth Dynamics of Conifer Tree Rings: Images of Past and Future Environments. Ecological Studies 183: 354 pp.

Cook E.R. & Kairiukstis L.A. (Editors) 1990: Methods of Dendrochronology. Kluwer Academic Publishers, 394 pp.

Hughes M.K., Kelly P.M., Pilcher J.R., Lamarche V.C., Jr. (Editors) 1982: Climate from tree rings. Cambridge University Press, 223 pp.

Fritts H.C. 1976: Tree Rings and Climate. Academic Press, 567 pp.